Tire for heavy goods vehicle having reinforced bead

ABSTRACT

Tyre ( 10 ) for a heavy goods vehicle comprising a radial carcass reinforcement ( 60 ) anchored in each of the beads ( 50 ) to an anchoring structure ( 700 ), comprising a circumferential reinforcement ( 70 ), the carcass reinforcement ( 60 ) being partially wrapped around the anchoring structure ( 700 ), the tyre ( 10 ) also comprising a coupling reinforcement ( 150 ) comprising a first part ( 151 ) in contact with the carcass reinforcement ( 60 ) and being extended by a second part ( 152 ) in contact with the anchoring structure ( 700 ) as far as a point ( 157 ) radially on the outside of the anchoring structure ( 700 ), located axially between the axially innermost point ( 702 ) and the axially outermost point ( 704 ) of the anchoring structure ( 700 ), the tyre ( 10 ) also comprising a stiffening reinforcement ( 160 ) surrounding the coupling reinforcement ( 150 ) and running radially on the inside of the anchoring structure ( 700 ) and of the coupling reinforcement ( 150 ), wherein the axially outside end point ( 166 ) of said stiffening reinforcement ( 160 ) is located at a radial distance DR from the radially innermost point ( 73 ) of the circumferential reinforcement ( 70 ), the radial distance DR being greater than or equal to 0.2 times and less than or equal to 0.6 times the distance DC between the radially outermost and radially innermost points ( 62, 63 ) of the carcass reinforcement, and wherein, radially on the outside of the anchoring structure ( 700 ), the minimum distance DT between the axially external portion ( 162 ) of the stiffening reinforcement ( 160 ) and the carcass reinforcement ( 60 ) is greater than or equal to 2 mm.

RELATED APPLICATIONS

This is a U.S. national stage of application No. PCT/EP2010/060861,filed on 27 Jul. 2010, which claims Priority to the French ApplicationNo.: 0955331, filed 30 Jul. 2009 and U.S. Application No. 61/255,402,filed 27 Oct. 2009 the contents of both of which are hereby incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to tires having a radial carcassreinforcement and designed to be fitted to heavy goods vehicles. Itrelates even more particularly to the bead structure of these tires.

BACKGROUND

A heavy goods vehicle tire comprises a crown portion that is extended oneach side by sidewalls ending in beads. Such a tire comprises aplurality of reinforcements including, in particular, a carcassreinforcement the role of which is to withstand the forces created bythe internal inflation pressure of the tire. This carcass reinforcementis situated in the crown and sidewalls of the tire and is anchored atits ends to suitable anchoring structures located in the beads. Thecarcass reinforcement is generally composed of a plurality ofreinforcing elements arranged parallel to one another and making anangle of close or equal to 90 degrees with the circumferential direction(in this case, the carcass reinforcement is said to be “radial”). Thecarcass reinforcement is usually anchored by being turned up around ananchoring structure having a suitable circumferential stiffness, inorder to form axially on the outside a turn-up portion of which thelength, measured for example with respect to the radially innermostpoint of the anchoring structure, is chosen to provide satisfactoryendurance to the tire during use. Axially between the turn-up portionand the main portion of the carcass reinforcement there are one or moreelastomer-based materials which provide mechanical coupling between thetwo portions of the carcass reinforcement.

In use, such a tire is mounted on a mounting rim comprising rim seatsdesigned to be in contact with the radially innermost parts of the beadsand, axially on the outside of each seat, a rim flange for fixing theaxial position of said bead when the tire is mounted and inflated to itsnominal pressure.

In order to make the tire withstand the mechanical stresses of rolling,it is known practice to provide additional bead reinforcements inparticular in the form of plies arranged against at least part of theturn-up portion of the carcass reinforcement.

During rolling, the tire beads are subjected to a large number ofbending cycles, as they wind around the rim flanges (i.e. they partlyadopt the geometry of said flanges). This bending results in larger orsmaller variations in curvature combined with variations in tension inthe bead reinforcements and in particular in the turn-up portion of thecarcass reinforcement. These same cycles induce compressive andextensile forces in the materials constituting the beads. Duringrolling, a cyclical circumferential displacement of the reinforcingelements of the reinforcement of the carcass reinforcement can also beseen in the sidewalls and the beads of the tire. A cyclicalcircumferential displacement is understood here to mean thatdisplacement occurs in one direction and in the opposite direction withrespect to a mean position of equilibrium each time the wheel rotates.

Rolling generates stresses and/or deformations in the materialsconstituting the bead, in particular the elastomers and moreparticularly those which are located in the immediate vicinity of theends of the reinforcements (the end of the turn-up portion of thecarcass reinforcement or the ends of the additional reinforcements).These stresses and/or deformations may lead to a more or lesssubstantial reduction in the service life of the tire.

This is because these stresses and/or deformations may cause detachmentand cracks near the ends of said reinforcements. Owing to the radialorientation of the reinforcing elements and to the nature of saidreinforcing elements (in general, these are metal cables) of which it ismade, the end of the turn-up portion of the carcass reinforcement isparticularly sensitive to this phenomenon.

The document published under the reference WO 20061013201-A1 describes atire bead structure in which the carcass reinforcement is no longerturned up by being partially wrapped around a bead wire but is wound atleast one complete revolution around an anchoring structure in each ofthe beads. In this manner, the end of the carcass reinforcement islocated in an area of the bead which is not subjected to strong cyclicalstresses; it is thus possible to increase the endurance of the beads.

However, while such a tire bead structure is effective from a mechanicalpoint of view, it is nonetheless still expensive and difficult toimplement using conventional industrial manufacturing means.

In a different approach, a means has been sought to prevent the risks ofbead deterioration by proposing a bead structure having sufficientstiffness to withstand the bending forces and the circumferentialmovements of the reinforcements during rolling which is also easy toimplement and economically attractive to produce on an industrial scale.

The document published under the reference WO 2008/107234-A1 describessuch a bead structure. The document discloses a heavy goods vehicle tirecomprising a tread extended transversely on each side by sidewallsending in beads designed to engage with a mounting rim. In addition,this tire comprises a radial carcass reinforcement formed from aplurality of reinforcing elements directed in a direction that makes anangle of at least 80 degrees with the circumferential direction.

This carcass reinforcement is anchored in each of the beads to ananchoring structure comprising a circumferential reinforcement aroundwhich a coating profiled element is formed of which the perimeter of theradial section comprises a part radially on the inside and a partradially on the outside, these two parts meeting at the two axiallyfurthest apart points of the perimeter of said coating profiled element.

Moreover, this carcass reinforcement is partially wrapped around thecoating profiled element of the anchoring structure, proceeding from theinside of the tire to the outside, the end of this carcass reinforcementbeing located on or near the perimeter of the coating profiled element.

This tire also comprises a first connecting reinforcement formed from aplurality of reinforcing elements directed in a direction that makes anangle of greater than or equal to 70 degrees with the circumferentialdirection. This first connecting reinforcement comprises a first part incontact with the carcass reinforcement between (i) a point radially onthe outside with respect to the perimeter of the coating profiledelement of the radially outermost anchoring structure and (ii) the endpoint of the carcass reinforcement, this first connecting reinforcementbeing extended beyond the end of the carcass reinforcement by a secondpart in contact with the coating profiled element as far as a pointlocated on the part radially on the outside of the perimeter of thecoating profiled element.

This tire furthermore comprises a second connecting reinforcementsurrounding the first connecting reinforcement and running radiallyunder the coating profiled element radially on the inside of said firstconnecting reinforcement in order to form an internal portion and anexternal portion, the internal portion being located axially on theinside with respect to the carcass reinforcement and the externalportion being located axially on the outside of said carcassreinforcement; the internal portion is in contact over a non-zero lengthwith the carcass reinforcement between a first end point of the firstportion and the end point of the first connecting reinforcement, theexternal portion being in contact with the carcass reinforcement fromone point to an end point of the external portion over a non-zerolength, these points being located radially outside the end points ofthe first connecting reinforcement.

This second connecting reinforcement is formed from a plurality ofreinforcing elements directed in a mean direction that makes an angle ofat most 50 degrees with the circumferential direction.

What distinguishes the architecture of this tire is, inter alia, thefact that the second connecting reinforcement is anchored around thebead anchoring structure while at the same time being coupled to thecarcass reinforcement axially on each side of this reinforcement, incombination with the end of the carcass reinforcement being positionedin the vicinity of the anchoring structure. In such a structure, the endof the carcass reinforcement is kept in an area subjected to fairly lowamounts of stress and deformation under running conditions and this endis moreover covered by at least the second reinforcement.

While such an architecture allows bead deterioration to be significantlyreduced, there is still an area subject to a high concentration ofcrack-initiating stresses radially on the inside of the anchoringstructure.

SUMMARY OF THE INVENTION

One object of the present invention is to further reduce the risks ofbead deterioration.

This object is achieved by a bead structure the carcass reinforcement ofwhich has no free end and which nevertheless has sufficient stiffness towithstand bending and deradialisation forces, this stiffness beingbrought about by additional reinforcing elements the ends of which, onthe axially outer side of the tire, are located in areas of lowdeformation so as to reduce the concentrations of crack-initiatingstresses.

More specifically, this object is achieved in accordance with one aspectof the present invention directed to a tire for a heavy goods vehicle,designed to be mounted on a rim, and comprising: a crown comprising acrown reinforcement surmounted by a tread; two sidewalls extending thecrown radially inwards; two beads radially inside the sidewalls anddesigned to engage with the rim, each bead comprising an anchoringstructure, the anchoring structure comprising a circumferentialreinforcement, the anchoring structure having in any radial section aradially innermost point, a radially outermost point, an axiallyinnermost point and an axially outermost point; and a radial carcassreinforcement comprising a plurality of reinforcing elements directed ina direction that makes an angle of at least 80 degrees with thecircumferential direction, the carcass reinforcement being anchored ineach of the beads to the anchoring structure, the carcass reinforcementbeing partially wrapped around the anchoring structure, passing axiallyfrom the inside to the outside of the tire, the end point of thiscarcass reinforcement being located on or near the anchoring structureand axially between the axially innermost point and the axiallyoutermost point of the anchoring structure.

The tire also comprises a coupling reinforcement formed from a pluralityof reinforcing elements directed in a direction that makes an angle ofgreater than or equal to 70 degrees with the circumferential direction,comprising a first part in contact with the carcass reinforcementbetween an end point which is radially on the outside with respect tothe radially outermost point of the anchoring structure and the endpoint of the carcass reinforcement, the coupling reinforcement beingextended beyond the end point of the carcass reinforcement by a secondpart in contact with the anchoring structure and as far as an end pointradially on the outside of the anchoring structure, the end point of thecoupling reinforcement being located axially between the axiallyinnermost point and the axially outermost point of the anchoringstructure.

The tire also comprises a stiffening reinforcement surrounding thecoupling reinforcement and running radially on the inside of theanchoring structure and of the coupling reinforcement so as to form anaxially internal portion and an axially external portion, the axiallyinternal portion being axially on the inside with respect to the carcassreinforcement and the axially external portion being axially on theoutside of said carcass reinforcement, the axially internal portionbeing in contact over a length LC with the carcass reinforcement betweenthe end point of said axially internal portion and the end point of thecoupling reinforcement, the end point being located radially on theoutside of the end point of the coupling reinforcement, this stiffeningreinforcement being formed from a plurality of reinforcing elementsdirected in a mean direction that makes an angle of less than or equalto 60 degrees and preferably less than or equal to 50 degrees with thecircumferential direction.

The axially outside end point of the stiffening reinforcement is locatedat a radial distance DR from the radially innermost point of thecircumferential reinforcement of the anchoring structure, the radialdistance DR being greater than or equal to 0.2 times the distance DCbetween the radially outermost point of the carcass reinforcement andthe radially innermost point of the same carcass reinforcement and lessthan or equal to 0.6 times the distance DC between the radiallyoutermost point of the carcass reinforcement and the radially innermostpoint of the same carcass reinforcement.

In addition, radially on the outside of the anchoring structure, theminimum distance DT between the axially external portion of thestiffening reinforcement and the carcass reinforcement is greater thanor equal to 2 mm.

By virtue of this location of the end of the stiffening reinforcement,the stresses to which the end of the stiffening reinforcement issubjected are limited and the formation of cracks is very significantlyslowed down.

According to a preferred embodiment, the stiffening reinforcementcomprises a first layer of reinforcing elements and a second layer ofreinforcing elements. Preferably, the reinforcing elements of said firstand second layers of reinforcing elements are textile threads, inparticular textile cords. With such threads it is possible to locate theend of the stiffening reinforcement at a great distance from theanchoring structure, in an area where the shear undergone by the rubbermixes and linked to bending of the bead is reduced and consequently therisk of cracks appearing in the rubber mixes is lessened. This highposition also provides the benefit of a reinforcement over the entireheight of the bead, and this restricts creeping of the rubber mixes ofthe bead when the latter is subjected to high operating temperatures. Itis more difficult to achieve this high position with a metalreinforcement since the ends of the stiffening reinforcement cords orcables still move, indenting the rubber mixes in this high area. As amatter of fact, the stiffer the cables the more pronounced thisindentation is. With textile threads, which are more flexible and lessaggressive than metal reinforcing elements, the indentation is slightand does not cause incipient cracks at the end of the reinforcingelement. However bending stiffness at the edge of a single-layer textilereinforcement is also weak compared with that of a single-layer metalreinforcement and proves to be insufficient to counter deradialisationof the carcass reinforcement. By coupling together two layers of textilethreads running in opposite directions, the bending stiffness at theedge is substantially higher and the two-layer stiffening reinforcementproduced in this way enables deradialisation movements of the carcassreinforcement and wear of the outer rubber mixes on the tire mountingrim flange to be effectively reduced.

Preferably, the first layer of reinforcing elements comprises aplurality of reinforcing elements directed in a mean direction thatmakes an angle of greater than or equal to +40 degrees and less than orequal to +50 degrees with the circumferential direction, and the secondlayer of reinforcing elements comprises a plurality of reinforcingelements directed in a mean direction that makes an angle of greaterthan or equal to −40 degrees and less than or equal to −50 degrees withthe circumferential direction. The inversion of the sign indicates thatthe reinforcing elements of the two layers must cross one another. Theseangles enable the compromise between coupling the two layers andcombating deradialisation to be optimized. Which of the layers has thepositive angle is immaterial.

Advantageously, the axially outside end point of said stiffeningreinforcement is located at a radial distance DR from the radiallyinnermost point of the circumferential reinforcement of the anchoringstructure, the radial distance DR being greater than or equal to 0.25times and less than or equal to 0.45 times the distance DC between theradially outermost point of the carcass reinforcement and the radiallyinnermost point of the same carcass reinforcement. Outside this range,the end of the stiffening reinforcement is in highly stressed areas suchas the bending area of the sidewall.

According to an advantageous embodiment, the anchoring structurecomprises a coating profiled element surrounding the circumferentialreinforcement, the perimeter of the radial section of the coatingprofiled element comprises a part radially on the inside and a partradially on the outside, said parts meeting at the axially innermost andaxially outermost points of the anchoring structure, and the end pointof the carcass reinforcement is located on or near the perimeter of thecoating profiled element. The existence of such a coating profiledelement enhances the adhesion between the anchoring structure and thecarcass reinforcement, on the one hand, and the coupling reinforcement,on the other.

According to an advantageous embodiment, the contact length LC of theaxially internal portion of the stiffening reinforcement is at least 20percent of the distance DY between the radially outermost end point ofthe axially internal portion of the stiffening reinforcement and theradially innermost point of the circumferential reinforcement of theanchoring structure. The contact length LC is thus sufficient for thestiffening reinforcement to effectively oppose deradialisation movementsof the carcass reinforcement during rolling-movements which can generatebead wear of the tire on the wheel.

Preferably, the distance DY between the radially outermost end point ofthe axially internal portion of the stiffening reinforcement and theradially innermost point of the circumferential reinforcement of theanchoring structure is greater than or equal to 15 percent and less thanor equal to 40 percent of the radial distance DC between the radiallyoutermost point of the carcass reinforcement and the radially innermostpoint of the same carcass reinforcement. The radially outermost endpoint of the axially internal portion of the stiffening reinforcement isthus sufficiently far from the areas of the bead and the sidewall whichare subject to substantial bending during rolling, and as a result theformation of cracks is prevented.

According to an advantageous embodiment, the reinforcing elements of thecoupling reinforcement and of the stiffening reinforcement are identicaland chosen from reinforcing elements of a textile nature. The use oftextile reinforcing elements for the coupling reinforcement greatlyfacilitates its wrapping around the anchoring structure.

It is advantageous to separate the axially internal portion of thestiffening reinforcement from the carcass reinforcement so as to reducethe shear stresses near the end point of said axially internal point, anelastomer being interposed between said reinforcements.

Advantageously, the stiffening reinforcement is formed from twodiscontinuous parts each constituting one of the portions, thesediscontinuous parts overlapping in a superposition area.

When the stiffening reinforcement is formed from two discontinuous partseach constituting one of the portions, and these discontinuous partsoverlap in a superposition area, it is advantageous to ensure that thesuperposition area is located in the vicinity of the coating profiledelement of the anchoring structure and that in any radial section thelength LK of the superposition area is at least half the axial distanceDA between the axially furthest apart points of the anchoring structure.

According to a particular embodiment, the coupling reinforcement isinterposed between the coating profiled element of the bead anchoringstructure and the carcass reinforcement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show diagrammatically a tire according to the prior art.

FIG. 3 shows diagrammatically and in radial section part of a tireaccording to an embodiment of the invention.

FIG. 4 shows a detail of FIG. 3.

FIGS. 5, 6 and 8 show diagrammatically and in radial section varioustire beads according to an embodiment of the invention.

FIG. 7 shows a detail of FIG. 6.

DETAILED DESCRIPTION OF THE DRAWINGS

It is important to distinguish between several different uses of theterm “radial” by persons skilled in the art. Firstly, the expressionrefers to a radius of the tire. It is within this meaning that a pointP1 is referred to as being “radially inside” a point P2 (or “radially onthe inside of” the point P2) if it is nearer to the axis of rotation ofthe tire than the point P2. Conversely, a point P3 is referred to asbeing “radially outside” a point P4 (or “radially on the outside of” thepoint P4) if it is further from the axis of rotation of the tire thanthe point P4. Progress in the direction of smaller (or larger) radii isreferred to as progress “radially inwards (or outwards)”. This meaningof the term also applies to radial distances.

By contrast, a thread or a reinforcement is said to be “radial” when thethread or the reinforcing elements of the reinforcement make an angle ofgreater than or equal to 80° and less than or equal to 90° with thecircumferential direction. It should be specified that in the presentdocument the term “thread” should be understood very broadly andincludes threads in the form of monofilaments, multifilaments, a cableor cord, a folded yarn or an equivalent assembly, no matter whatmaterial the thread is made of or the surface treatment performed topromote its adhesion to the rubber.

Finally, the expression “radial section” is understood here to be asection on a plane which includes the axis of rotation of the tire.

An “axial” direction is a direction parallel to the axis of rotation ofthe tire. A point P5 is referred to as “axially inside” a point P6 (or“axially on the inside of” the point P6) if it is nearer the mid-planeof the tire than the point P6. Conversely, a point P7 is referred to asbeing “axially outside” a point P8 (or “axially on the outside of” thepoint P8) if it is further from the mid-plane of the tire than the pointP8. The “mid-plane” of the tire is the plane perpendicular to the axisof rotation of the tire and located equidistant from the circumferentialreinforcements of each bead.

A “circumferential” direction is a direction perpendicular both to aradius of the tire and to the axial direction. A “circumferentialsection” is a section on a plane perpendicular to the axis of rotationof the tire.

“Rolling surface” is understood here to mean all the points of the treadof a tire that are likely to come into contact with the ground when thetire is rolling.

The expression “rubber compound” denotes a rubber composition comprisingat least an elastomer and a filler.

In order to facilitate reading of the description of the embodimentsshown in the figures, the same references are used to denote elementshaving identical structures.

FIG. 1 shows diagrammatically a tire 10 according to the prior art. Thetire 10 comprises a crown comprising a crown reinforcement (not visiblein FIG. 1) surmounted by a tread 30, two sidewalls 40 extending thecrown radially inwards, and two beads 50 radially inside the sidewalls40.

FIG. 2 shows diagrammatically a partial perspective view of another tire10 according to the prior art and illustrates the various components ofthe tire. The tire 10 comprises a carcass reinforcement 60 consisting ofthreads 61 coated with a rubber mix, and two beads 50 each comprisingcircumferential reinforcements 70 (in this case bead wires) which keepthe tire 10 on the rim (not shown). The carcass reinforcement 60 isanchored in each of the beads 50. The tire 10 also comprises a crownreinforcement comprising two plies 80 and 90. Each of the plies 80 and90 is reinforced by filamentary reinforcing elements 81 and 91 which areparallel in each layer and crossed from one layer to the next, makingangles of between 10° and 70° with the circumferential direction. Thetire also comprises a hooping reinforcement 100 arranged radially on theoutside of the crown reinforcement, this hooping reinforcement beingformed from reinforcing elements 101 directed circumferentially andwound in a spiral. A tread 30 is placed on the hooping reinforcement; itis by means of this tread 30 that the tire 10 makes contact with theroad. The tire 10 shown is a “tubeless” tire: it comprises an “innerliner” 110 made of a rubber composition impermeable to the inflation gasand covering the inner surface of the tire.

FIG. 3 shows diagrammatically and in radial section part of a tire 10according to an embodiment of the invention, of size 295/60R22.5. It isa heavy goods vehicle tire designed to be mounted on a rim (not shown).The tire 10 comprises a crown comprising a crown reinforcement, formedby plies 80 and 90, sandwiched between reinforcing plies 120 and 130.The reinforcing ply 120 protects the carcass reinforcement 60 fromcompression and the reinforcing ply 130 protects the crown reinforcementfrom punctures and impacts. The latter ply is surmounted by a tread 30.The tire 10 also comprises two sidewalls 40 extending the crown radiallyinwards and two beads 50 radially inside the sidewalls and designed toengage with the rim. Each bead comprises an anchoring structure 700, theanchoring structure comprising a circumferential reinforcement 70. Inthe present case, the reinforcement 70 is a bead wire composed of aplurality of circumferentially wound metallic wires. As shown in FIG. 4,the anchoring structure 700 has in any radial section a radiallyinnermost point 703, a radially outermost point 701, an axiallyinnermost point 702 and an axially outermost point 704. The radiallyoutermost point 71 and the radially innermost point 73 of thecircumferential reinforcement 70 are also indicated. If the geometry ofthe anchoring structure 700 is such that a plurality of points qualifyas axially/radially innermost/outermost, any one of these points can beselected. The anchoring structure also comprises a coating profiledelement 75, in this case a nylon 140/2 fabric. The nylon cords of thecoating profiled element 75 are coated with rubber mix having a modulusof elasticity at 10 percent elongation (at 20° C.) of greater than 5MPa. The cords are spaced 1 mm apart and directed in a direction thatmakes an angle of greater than or equal to 50 degrees with thecircumferential direction.

The tire 10 also comprises a radial carcass reinforcement 60 comprisinga plurality of metal cables formed from a number of elemental threadsmeasuring 18/100 mm. These cables are embedded in a rubber mix anddirected in a direction that makes an angle of greater than or equal to80 degrees with the circumferential direction. The carcass reinforcement60 is anchored in each of the beads to the anchoring structure 700:specifically, the carcass reinforcement 60 is partially wrapped aroundthe anchoring structure 700, passing axially from the inside to theoutside of the tire. The carcass reinforcement 60 thus follows theprofile of part of the perimeter of the coating profiled element 75 andis mechanically coupled to this coating profiled element by adhesion ofthe material of which the coating profiled element is composed and thematerial coating the reinforcing elements of the carcass reinforcement60. The end point 65 of this carcass reinforcement 60 is located on ornear the anchoring structure 700 and axially between the axiallyinnermost point 702 and the axially outermost point 704 of the anchoringstructure. When the end point 65 of the carcass reinforcement is said tobe located “near” the anchoring structure 700, this should be understoodas meaning that the minimum distance between the end point 65 and theanchoring structure 700 is less than or equal to 4 mm.

Moreover, an apex 140 made of rubber mix is provided in the bead. Thematerial of this profiled element is preferably chosen such that it hasa modulus of elasticity at 10 percent elongation (at 20° C.) of between2 and 5 MPa (in this case 4 MPa).

The tire 10 also comprises a coupling reinforcement 150 formed from aplurality of cord reinforcing elements made of aramid 160×3 directed ina direction that makes an angle of greater than or equal to 70 degreeswith the circumferential direction. The aramid cords of the couplingreinforcement 150 are coated in rubber mix having a modulus ofelasticity at 10 percent elongation (at 20° C.) of greater than 5 MPa.The cords are spaced 1.25 mm apart. This coupling reinforcement 150comprises a first part 151 and a second part 152. The first part 151consists of the part of the coupling reinforcement 150 in contact withthe carcass reinforcement. This first part 151 extends between (i) anend point 155 radially on the outside with respect to the radiallyoutermost point 701 of the anchoring structure 700 (see FIG. 4) and (ii)the end point 65 of the carcass reinforcement 60. The couplingreinforcement 150 is extended beyond the end point 65 of the carcassreinforcement 60 by a second part 152 which is in contact with theanchoring structure 700 as far as an end point 157 radially on theoutside of the anchoring structure 700. The end point 157 of thecoupling reinforcement 150 is located axially between the axiallyinnermost point 702 and the axially outermost point 704 of the anchoringstructure 700. The boundary between the first part 151 and the secondpart 152 of the coupling reinforcement is considered to be located atthe axial position of the end point 65 of the carcass reinforcement 60.

Finally, the tire 10 comprises a stiffening reinforcement 160surrounding the coupling reinforcement 150 and running radially on theinside of the anchoring structure 700 and of the coupling reinforcement150 so as to form an axially internal portion 161 and an axiallyexternal portion 162. The axially internal portion 161 is the portion ofthe stiffening reinforcement 160 axially on the inside with the respectto the carcass reinforcement 60 and the axially external portion 162 isthe portion of the stiffening reinforcement 160 axially on the outsideof the carcass reinforcement 60. The boundary between the axiallyinternal portion 161 and the axially external portion 162 is consideredto be located at the axial position of the radially innermost point 63of the carcass reinforcement 60.

When the carcass reinforcement 60 comprises a number of radiallyinnermost points, any one of these points can be selected. The axiallyinternal portion 161 is in contact over a length LC with the carcassreinforcement 60, between the end point 165 of said axially internalportion 161 and the end point 155 of the coupling reinforcement 150, theend point 165 being located radially on the outside of the end point 155of the coupling reinforcement 150. It should be noted, moreover, thatnear the end point 165 of the axially internal portion 161, the latteris locally separated from the carcass reinforcement so as to reduce theshear stresses in this area, some of the rubber mix being interposedbetween the reinforcements.

In the present case, the stiffening reinforcement 160 comprises a firstlayer of textile reinforcing elements 167 and a second layer of textilereinforcing elements 168. Its axially internal portion 161 thus consistsof two layers 261 and 361, as is the axially external portion 162 whichconsists of the layers 262 and 362.

The first layer of reinforcing elements 167 comprises a plurality ofreinforcing elements directed in a mean direction that makes an angle of+45 degrees with the circumferential direction and the second layer ofreinforcing elements 168 comprises a plurality of reinforcing elementsdirected in a mean direction that makes an angle of −45° with thecircumferential direction. This choice of angles has in particular theeffect of facilitating the manufacture and turning up of the stiffeningreinforcement 160 around the reinforcement 70. It also allows thederadialisation of the carcass reinforcement 60 to be reducedeffectively.

The ends of the first layer of reinforcing elements 167 and the ends ofthe second layer of reinforcing elements 168 are offset by at least 5 mmso as to reduce the stressing of the surrounding rubber by indentation.

The axially outside end point 166 of the stiffening reinforcement 160 islocated at a radial distance DR from the radially innermost point 73 ofthe circumferential reinforcement 70 of the anchoring structure 700. Ina tire according to an embodiment of the invention, the radial distanceDR is greater than or equal to 0.2 times and less than or equal to 0.6times the distance DC between the radially outermost point 62 of thecarcass reinforcement 60 and the radially innermost point 63 of the samecarcass reinforcement. In the present case, DC=140 mm, DR=53 mm andDR=0.38×DC.

Radially on the outside of the anchoring structure 700, in any radialsection, the minimum distance DT between the axially external portion162 of the stiffening reinforcement 160 and the carcass reinforcement 60is greater than or equal to 2 mm (in this case DT=4 mm). This minimumdistance is measured perpendicularly to the carcass reinforcement 60.

The contact length LC (in this case LC=13 mm) of the axially internalportion 161 of the stiffening reinforcement 160 is in this case equal to37 percent of the distance DY between the radially outermost end point165 of the axially internal portion of the stiffening reinforcement 160and the radially innermost point 73 of the circumferential reinforcement70 of the anchoring structure 700 (in this case DY=35 mm).

The distance DY is furthermore equal to 25 percent of the radialdistance DC between the radially outermost point 62 of the carcassreinforcement and the radially innermost point 63 of the same carcassreinforcement.

FIG. 5 shows diagrammatically and in radial section a variant of a tirebead according to an embodiment of the invention. In contrast to thebead of the tire 10 in FIG. 3, the coating profiled element 75 comprisesboth a retention reinforcement 751 and a rubber padding 752 made ofrubber mix and surrounding the circumferential reinforcement 70. Theretention reinforcement 751 may be produced from a stiff rubber mix(having a modulus of elasticity at 10 percent and 20° C. of greater than10 MPa) or of a composite, comprising aramid or nylon textilereinforcing elements and rubber mix, e.g. rubber mix of the same type asthe rubber mix embedding the reinforcing elements of the couplingreinforcement. In each radial section, the perimeter of the coatingprofiled element 75 comprises a part radially on the inside and a partradially on the outside, said parts meeting at the axially innermost andaxially outermost points 702, 704 of the anchoring structure. Again, theend point 65 of the carcass reinforcement is located on or near theperimeter of the coating profiled element 75.

FIG. 6 shows diagrammatically and in radial section another variant of atire bead according to an embodiment of the invention. In this case,over most of its extent the stiffening reinforcement comprises only onelayer but it is formed from two discontinuous parts 161 and 162, thesediscontinuous parts overlapping in a superposition area. Thissuperposition area is located in the vicinity of the coating profiledelement of the anchoring structure, which means that the distance DUbetween the axially inner end 163 of the axially outer strand 162 of thestiffening reinforcement 160 and the radially innermost point of theanchoring structure 700 is less than 1.5 DR (see FIG. 3).

In any radial section, the length LK (indicated by means of adouble-headed arrow in FIG. 7; in this case LK=15 mm) of thesuperposition area, defined as the curvilinear length of the path of theinterface between the two discontinuous parts 161 and 162, is at leasthalf the axial distance DA (see FIG. 7; in this case DA=19 mm) betweenthe axially furthest apart points 702 and 704 of the anchoring structure700. These points 702 and 704 are obtained by constructing tangents T1and T2 to the anchoring structure 700, said tangents being perpendicularto the axis of rotation of the tire.

This variant is advantageous because it allows the materials of the twodiscontinuous parts 161 and 162 to be differentiated, either byemploying reinforcing elements of differing kinds (for example textilereinforcing elements for one part and metal reinforcing elements for theother) or by employing differing coating materials, or a combination ofthe two. It also allows to improve manufacturing as there is greaterprecision in the position of the components and reinforcements and areduction in the space taken up at manufacturing stations.

FIG. 8 shows diagrammatically and in radial section another variant of atire bead according to an embodiment of the invention. In this case, thecoupling reinforcement 150 is interposed between the coating profiledelement 75 of the bead anchoring structure 700 and the carcassreinforcement 60. The end 65 of the carcass reinforcement 60 is thuspositioned between the coupling reinforcement 150 and the stiffeningreinforcement 160. This arrangement ensures better mechanical integrityof the carcass reinforcement in each bead and prevents the reinforcingelements of this reinforcement from coming into contact with thecircumferential reinforcement 70 while the tire is in use.

In a heavy goods vehicle tire of size 295/60 R 22.5, the novel geometryof the bead improved the distance covered in a flywheel endurance testby more than 20% with respect to the tires of the document WO2008/107234-A1. The test consists in rolling the tires on a steelflywheel under conditions which bring about a great increase in thetemperature of the bead. It ends with the unwinding of the carcassreinforcement.

1.-13. (canceled)
 14. A tire for a heavy goods vehicle, designed to bemounted on a rim, and comprising: a crown comprising a crownreinforcement surmounted by a tread; two sidewalls extending the crownradially inwards; two beads radially inside the sidewalls and designedto engage with the rim, each bead comprising an anchoring structure, theanchoring structure comprising a circumferential reinforcement, theanchoring structure having in any radial section a radially outermostpoint, an axially innermost point and an axially outermost point; aradial carcass reinforcement comprising a plurality of reinforcingelements directed in a direction that makes an angle of greater than orequal to 80 degrees with the circumferential direction, the carcassreinforcement being anchored in each of the beads to the anchoringstructure, the carcass reinforcement being partially wrapped around theanchoring structure, passing axially from the inside to the outside ofthe tire, the end point of this carcass reinforcement being located onor near the anchoring structure and axially between the axiallyinnermost point and the axially outermost point of the anchoringstructure; a coupling reinforcement formed from a plurality ofreinforcing elements directed in a direction that makes an angle ofgreater than or equal to 70 degrees with the circumferential direction,comprising a first part in contact with the carcass reinforcementbetween an end point which is radially on the outside with respect tothe radially outermost point of the anchoring structure and the endpoint of the carcass reinforcement, the coupling reinforcement beingextended beyond the end point of the carcass reinforcement by a secondpart in contact with the anchoring structure as far as an end pointradially on the outside of the anchoring structure, the end point of thecoupling reinforcement being located axially between the axiallyinnermost point and the axially outermost point of the anchoringstructure; and a stiffening reinforcement surrounding the couplingreinforcement and running radially on the inside of the anchoringstructure and of the coupling reinforcement so as to form an axiallyinternal portion and an axially external portion, the axially internalportion being axially on the inside with respect to the carcassreinforcement and the axially external portion being axially on theoutside of the carcass reinforcement, the axially internal portion beingin contact over a length LC with the carcass reinforcement between theend point of said axially internal portion and the end point of thecoupling reinforcement, the end point of said axially internal portionbeing located radially on the outside of the end point of the couplingreinforcement, this stiffening reinforcement being formed from aplurality of reinforcing elements directed in a mean direction thatmakes an angle of less than or equal to 60 degrees with thecircumferential direction, wherein the axially outside end point of saidstiffening reinforcement is located at a radial distance DR from theradially innermost point of the circumferential reinforcement of theanchoring structure, the radial distance DR being greater than or equalto 0.2 times the distance DC between the radially outermost point of thecarcass reinforcement and the radially innermost point of the samecarcass reinforcement and less than or equal to 0.6 times the distanceDC between the radially outermost point of the carcass reinforcement andthe radially innermost point of the same carcass reinforcement, andwherein, radially on the outside of the anchoring structure, the minimumdistance DT between the axially external portion of the stiffeningreinforcement and the carcass reinforcement is greater than or equal to2 mm.
 15. The tire of claim 14, wherein said stiffening reinforcementcomprises a first layer of reinforcing elements and a second layer ofreinforcing elements.
 16. The tire of claim 15, wherein the first layerof reinforcing elements comprises a plurality of reinforcing elementsdirected in a mean direction that makes an angle of greater than orequal to +40 degrees and less than or equal to +50 degrees with thecircumferential direction, and wherein the second layer of reinforcingelements comprises a plurality of reinforcing elements directed in amean direction that makes an angle of greater than or equal to −40degrees and less than or equal to −50 degrees with the circumferentialdirection.
 17. The tire of claim 14, wherein the axially outside endpoint of said stiffening reinforcement is located at a radial distanceDR from the radially innermost point of the circumferentialreinforcement of the anchoring structure, the radial distance DR beinggreater than or equal to 0.25 times the distance DC between the radiallyoutermost point of the carcass reinforcement and the radially innermostpoint of the same carcass reinforcement and less than or equal to 0.45times the distance DC between the radially outermost point of thecarcass reinforcement and the radially innermost point of the samecarcass reinforcement.
 18. The tire of claim 14, wherein the anchoringstructure comprises a coating profiled element surrounding thecircumferential reinforcement, wherein the perimeter of the radialsection of the coating profiled element comprises a part radially on theinside and a part radially on the outside, said parts meeting at theaxially innermost and axially outermost points of the anchoringstructure, and wherein the end point of the carcass reinforcement islocated on or near the perimeter of the coating profiled element. 19.The tire of claim 14, wherein the contact length LC of the axiallyinternal portion of the stiffening reinforcement is at least 20 percentof the distance DY between the radially outermost end point of theaxially internal portion of the stiffening reinforcement and theradially innermost point of the circumferential reinforcement of theanchoring structure.
 20. The tire of claim 14, wherein the distance DYbetween the radially outermost end point of the axially internal portionof the stiffening reinforcement and the radially innermost point of thecircumferential reinforcement of the anchoring structure is greater thanor equal to 15 percent and less than or equal to 40 percent of theradial distance DC between the radially outermost point of the carcassreinforcement and the radially innermost point of the same carcassreinforcement.
 21. The tire of claim 14, wherein the reinforcingelements of said first and second layers of reinforcing elements aretextile threads.
 22. The tire of claim 14, wherein the reinforcingelements of the coupling reinforcement and of the stiffeningreinforcement are identical and chosen from reinforcing elements of atextile nature.
 23. The tire of claim 14, wherein the axially internalportion of the stiffening reinforcement is locally separated from thecarcass reinforcement so as to reduce the shear stresses near the endpoint of said axially internal point, an elastomer being interposedbetween said reinforcements.
 24. The tire of claim 14, wherein thestiffening reinforcement is formed from two discontinuous parts eachconstituting one of the portions, these discontinuous parts overlappingin a superposition area.
 25. The tire of claim 18, wherein thestiffening reinforcement is formed from two discontinuous parts eachconstituting one of the portions, these discontinuous parts overlappingin a superposition area, wherein the superposition area is located inthe vicinity of the coating profiled element of the anchoring structureand wherein in any radial section the length LK of the superpositionarea is at least half the axial distance DA between the axially furthestapart points of the anchoring structure.
 26. The tire of claim 14,wherein the coupling reinforcement is interposed between the coatingprofiled element of the bead anchoring structure and the carcassreinforcement.